When did you do your Christmas food shopping this year?

According to one of Britain's leading supermarket chains, Morrisons, the optimum time to go shopping for perishable food for Christmas was in a window between 6:30am and 7:30am on December 23rd. 

This suggestion was the result of some analysis of footfall at stores, and also used arguments about the freshness of perishable foods.  Because the stores receive deliveries in the small hours, and the fresh deliveries are stacked on the shelves early in the day, the early shoppers will have fresh goods, and there will be a large number of assistants working in the shop to help customers.  Also, footfall statistics show that this hour is not a popular time for shopping, so there will be fewer customers to battle with. 

As the result was announced in the news media the previous day, one wonders how many people changed their behaviour and did their food shopping in that time window this year.  I don't know if enough people did so to make the time non-optimal. 

I confess that I did consider suggesting to Tina that we might change our plans ...

But we did observe an interesting phenomenon when we turned up at our nearest supermarket where we planned to use a discount voucher before it expired.  It was 10am, and the car park was full.  All the checkouts were busy.  It took us about 45 minutes to complete our shopping, and by then the queues at the checkouts had almost gone, and the car park had plenty of space.  We concluded that many people had set out to shop in the 9am to 10am window ... maybe the rush had started earlier, but the observation of our shopping time, the queues and congestion suggested that many shoppers were coming first thing after breakfast.  (We felt smug, as we had been swimming for nearly an hour first thing after breakfast, before shopping.)  So, maybe there is another good window for shopping if you arrive at about 10:30am?

And, late this afternoon, after the crib service at church, we cycled to the same store, on the lookout for bargains at the end of the trading day.  (Yes, we did find some food that had been reduced in price.)  We had expected that most customers would have finished their purchasing, but it wasn't so.  There were queues for the car park, and busy checkouts.  It was busier than in the last two years, when we have also wandered up after the crib service, seeking bargains.  (Even the cycle racks were full.) 

Modelling customer demand for this supermarket would be interesting.  We got the impression that customers have been adapting the time when they shop - in response to their own and other people's experience?  If so, how does a modeller make forecasts?  It is a reminder that operational research modelling that involves people and their actions needs to acknowledge the complexity of people's psychology.  As is often the case, modelling humans is much more complex than modelling machines!


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